1. Field of the Invention
The invention relates to a light-emitting element, specifically, a light-emitting element with porous light-emitting layers.
2. Description of the Related Art
In recent years, as the price of a light-emitting diode becomes cheaper and cheaper, various application products utilizing the properties of the light-emitting diode such as thin, light, short and small, power-saving, and multi-colorizing, become more and more popular, such as in various assistant back lights for electronic instrument decoration, automobile instrument panels, public decorative lamps, various indoor indicator lights, fascia advertisement lamp and the like. Looking into the future, it is not a dream that all of the existing light-emitting elements will be substituted by solid light-emitting diodes.
Reviewing the development history of the light-emitting diode, the earliest light-emitting layer structure is a simple P and N junction, but the efficiency is poor since the chance for an electron and a hole to recombine is not so high. Since it has been known how to utilize quantum engineering or Energy band Gap engineering to make a light-emitting structure with a quantum well structure having a heterogeneous interface, the light-emitting efficiency of a light-emitting diode is thus improved greatly.
With reference to FIG. 1, a conventional quantum well light-emitting layer 10 has a quantum well structure 12, a first barrier layer 11 and a second barrier layer (not shown). The first barrier layer 11 is located below the quantum well structure 12, and the second barrier layer is located above the quantum well structure 12. In order to utilize a low energy band gap material (the quantum well structure 12) grown within a limited thickness, the quantum well light-emitting layer 10 comprises in the upper and lower layers having higher energy band gap materials (the first barrier layer 11 and the second barrier layer). In the view of the energy band gap, this structure may provide a carrier trap in one-dimensional space, so the carrier can be effectively trapped within the quantum well structure having the low energy band gap.
However, the disadvantage is that although most of the carriers can be captured and hence trapped in this quantum well without escaping, this carrier still has the ability to move in two-dimensional space, therefore resulting in the performance of the quantum well to be limited, including the disadvantages that the driving voltage cannot be further decreased, the anti-static electricity ability cannot be elevated effectively, and the light-emitting efficiency may be limited by the limited carrier recombination efficiency of the quantum well. Moreover, although the light-emitting diode has become a widely available commercial product to date, the light-emitting diode found in the market is still limited to the property of single chip and single wavelength.
Therefore, there is a necessity to provide an innovated and progressive light-emitting element to solve the problems described above.